TabbarController child controller always return nil - Swift 4

Question

I am trying to access the objects from child controller but it always returns nil. Please check the below code.

let mainStoryboard = UIStoryboard(name: "Main", bundle: Bundle.main)
let vc: UITabBarController = mainStoryboard.instantiateViewController(withIdentifier: "TabBarController") as! UITabBarController
vc.selectedIndex = 2
let vc1 = vc.viewControllers?[2] as? FormViewController //this line returns nil
vc1?.fillUserData(dataDic: convertJsonStringToDictionary(jsonString: decodedURL))
vc1?.formViewDelegate = self
self.present(vc, animated: true, completion: nil)

Please shed some light.

It's probably nil because the 3rd view controller isn't a `FormViewController`. Maybe it's a navigation controller. — rmaddy, Sep 09 '18 at 21:30
Am sure third view Controller is formviewcontroller and it's embed in navigation controller. — Mac_Play, Sep 09 '18 at 21:31
That's my whole point. `vc.viewControllers?[2]` is *not* a `FormViewController`, it's a `UINavigationController`. That is why you get `nil`. — rmaddy, Sep 09 '18 at 21:32

score 2 · Answer 1 · answered Sep 09 '18 at 21:37

Based on your comments, the 3rd tab is actually a UINavigationController which has the FormViewController as its rootViewController.

Update your code as:

if let nc = vc.viewControllers?[2] as? UINavigationController, let vc1 = nc.topViewController as? FormViewController {
    vc1.fillUserData(dataDic: convertJsonStringToDictionary(jsonString: decodedURL))
    vc1.formViewDelegate = self
}

score 1 · Answer 2 · answered Sep 09 '18 at 21:33

You can try

let nav = vc.viewControllers?[2] as? UINavigationController
let vc1 = nav?.topViewController as? FormViewController

note : you should not access any UI element here

vc1?.fillUserData(dataDic: convertJsonStringToDictionary(jsonString: decodedURL))

as it would crash the app

TabbarController child controller always return nil - Swift 4

2 Answers2